Underground loop-antenna



E. C. HANSON.

UNDERGROUND LOOP ANTENNA.

APPLICATION FILED MAR. 19. 1919.

1,373,61 2. Patented Apr. 5, 1921.

W1 TNESS: v INVENTOR.

umrao STATES EABL G. HANSON, OF WASHINGTON, DISTRICT OF COLUMBIA.

j UNDERGROUND LOOP-ANTENNA.

Specification of Letters Patent.

Patented Apr. 5.11921.

- l Application filed March 19, 1919. Serial No. 283,517.

T all whom it may concern:

Be it known that I, EARL G. Hanson, a citizen of the United States, and residentof Washington, District of Columbia, have 1n- 5 vented a new and useful Improvement in Underground Loop-Antennae, of whlch the following is a specification.

My invention relates to underground antenna systems for receiving radio signals,

and more particularly to underground loop forms of antennae;

The object of this invention is to provide a loop antenna adapted to be incased in a conduit and buried beneath the earth.

A further object of the invention is to provide such an underground loop antenna with filter coils inserted at intervals in the. turns of the loop to prevent responseto shock impulses produced by stray waves.

Referring to the drawings,

Figure 1 shows diagrammatically an underground vertical loop antenna;

Fig. 2 is a modification of Fig. 1 and indicates an underground loop antenna arranged in a horizontal plane below the surface of the earth.

Referring now more particularly to Fig. 1, reference character 2 represents a conduit buried in the earth 1. The conduit 2 is positioned vertically beneath the earth and incloses a number of convolutions of cable terminating at 3 and 4. Suitably located at intervals in the turns of the loop are filter coils 5 for the purpose to be more fully described hereinafter.

Fig. 2 represents a loop antenna system similar to that disclosed in Fig. 1, wherein the plane of the looped turns is parallel to the earths surface.

This loop system is connected. to suitable receiving apparatus at terminals 3 and 4. While the system has been described for use in conjunction with receiving apparatus, it is obvious that the antenna could be connected at 3 and 4 with radio transmitting apparatus and operated as a transmitting antenna. In Figs. 1 and 2, the loop system is shown as being undergroundrbut it is well understood by those skilled in the. art

to that such a loop antenna system can be submerged in water.

In Figs. 1 and 2, the loop antenna systems are shown buried in a conduit. This conduit may be of any suitable material. In some cases it would be feasible to employ heavy insulated binding around the convolutions of the loop. I 3

Considering the phenomenon of induced currents in the vertical loop c0il, Fig. 1, from progressing radiated wave trains perpendicular to the surface of the earth, it is well known in the art that radiated waves do not penetrate earth or water to iany'appreciable depth. To utilize this phenomenon in an underground loop system,gthe coil shown in Fig. 1 is constructed of such dimensions and placed at such a depth' as to allow only the top convolutions to be cut by the progressing wave trains, thus inducing currents which will actuate receiving apparatus connected to the terminals 3 and 4.

In Fig. 2 the progressing radiated perpendicular wave trains will induce currents in the turns of the horizontal loop and thereby actuate receiving apparatus connected to the terminals 8 and 4.

The filter coils 5 while not absolutely necessary are shown in the turns of the loop for the purpose of rendering the antenna irresponsive to any undesired frequency or shock excitation.

Resonant currents produced by passing wave trains of a definite frequency pass freely through the filter coils 5, while shock impulses produced by stray waves or 'waves of undesired frequencies are choked or filtered out. By filter coils it will be understood by those versed in the art is meant impedance or retardation coils represented at 5 throughout the several figures.

What I claim is 1. An underground antenna system for radio signaling comprising a looped coil inclosed in a conduit and arranged perpendicularly to the surface of the earth, and means electrically connected in the convolutions of the loop for substantially eliminatini response to strays. 1

2. p n underground antenna system for radio signaling comprising a looped coil having a plurality of turns positioned per- Q gamma pendicularly to the surface of the earth closed in a conduit and buried beneath the arranged below said surface and a series of surface of the earth and including a series filter coils inserted at several points in the of inductance coils Within the turns thereof 10 turns of the looped coil for substantially whereby response to shock excitation is sub- 5 eliminating shock impulses in said coil. stantially eliminated.

3. An underground antenna system for In testimony whereof I afiix my signature. radio signaling comprising a looped coil in; EARL C. HANSON. 

